Calculation & Generation Results
About This Tool
Calculate RF coaxial cable signal attenuation (dB loss per 100 ft and total run loss), velocity factor, and remaining transmitter power across RG-6, RG-58, RG-8X, LMR-400, and Heliax.
Frequently Asked Questions
Why does coaxial cable loss increase with frequency?
Signal attenuation increases with the square root of frequency due to the 'skin effect' (RF current forces itself into an increasingly thin outer layer of the copper conductor, raising AC resistance) and dielectric molecular heating losses.
What does 3 dB of cable loss mean in actual transmitter power?
A 3 dB signal loss cuts your delivered transmitter power in half (50% lost as heat). A 6 dB loss reduces power by 75% (only 25% reaches the antenna).
What is Cable Velocity Factor (VF)?
Velocity factor is the speed at which electromagnetic waves travel through the cable compared to the speed of light in a vacuum. Foam polyethylene dielectrics achieve a VF of 82% to 85%, while solid polyethylene operates at approximately 66%.
Why is LMR-400 preferred over RG-58 for VHF and UHF?
At 440 MHz (70cm band), a 100-foot run of thin RG-58 loses over 10.5 dB of signal (delivering less than 9% of your power to the antenna). Low-loss LMR-400 loses only 2.7 dB, delivering over 53% of power to the antenna.